In these circumstances, with no load, Q2 would be conducting 46mA while whitstandings 45V between C and E, so it would be dissipating more than 2 watts and would porbably blow after a few seconds.

There are other ways to get such a circuit to work properly, for example, by adding a PNP gain stage with its emitter connected to the input, its base driven with Q2 and its collector driving the base of Q1. It would make frequency stabilisation harder due to the additional pole, though.

Originally posted by Eva In these circumstances, with no load, Q2 would be conducting 46mA while whitstandings 45V between C and E, so it would be dissipating more than 2 watts and would porbably blow after a few seconds.

Yes you are right, Q2 as to less Power.
I thing more current Gain for Q1 like a Darlington NPN Transistor solve the work.
And with Iq ~ 3mA it ok ?